1. Field of the Invention
The present invention relates in general to data transfer methods, and more particularly to a data transfer method based on inter-node protocol interfacing.
2. Description of the Prior Art
The 1394 standard was published in 1986 as a digital link standard by Apple computer technical staff and thereafter adopted as a base of the IEEE1394 standard in 1995. The IEEE1394 standard is an international standard for the implementation of a high-speed serial bus structure which is capable of supporting both isochronous (real-time) and asynchronous transfer modes. This IEEE1394 standard provides a high-speed serial bus for interconnecting digital devices, which is implemented through an IEEE1394 serial bus network interface card (module). The IEEE1394 standard also provides an interface standard for an inter-digital node transfer technique which is capable of interconnecting multimedia, such as a communication node, a computer and an electric appliance, via a single network and effecting transmission/reception of data from the multimedia at a high rate ranging from 100 Mbps to 1 Gbps.
A cable prescribed in the IEEE1394 standard is able to interface isochronous data at a high-bandwidth, and it is thinner in thickness than other cables. The IEEE1394 standard further provides a multimedia operating characteristic capable of adding a new digital node or deleting an existing digital node even when existing digital nodes connected to the IEEE1394 cable are active.
The IEEE1394 serial bus provides the excellent transfer rate and bidirectional communication performance over a universal serial bus (USB) which is being highlighted as another multimedia standard. That is, the IEEE1394 serial bus can process data at three types of transfer rates, or 98.304 Mbps, 196.608 Mbps and 393.216 Mbps, according to transfer modes to smoothly transfer digital audio or moving picture information. In this regard, the IEEE1394 serial bus is able to connect the multimedia nodes to the peripheral nodes such as a scanner, a digital camera, a digital video camera, etc. The three transfer rates are compatible with one another. For example, the 393.216 Mbps transfer mode may support both the 98.304 Mbps and 196.608 Mbps transfer modes. The excellent bidirectional communication performance of the IEEE1394 serial bus enables the peripheral devices, or nodes, each containing IEEE1394 serial bus network interface cards (modules) to transmit and receive data in a multimedia application field such as a computer-based video teleconference.
FIG. 1 shows a general IEEE1394 serial bus network with a plurality of nodes interconnected via an IEEE1394 serial bus according to the IEEE1394 standard. Each of the nodes comprises an IEEE1394 serial bus network interface card (module), not shown, for transferring output data from the associated node to a different one of the nodes to record or display it. The nodes are interconnected in a point-to-point manner through the IEEE1394 serial bus network interface cards. Namely, an audio unit 100, digital television (DTV) 102, set-top box 104, computer 106, printer 108, scanner 110 and digital video disk read only memory (DVD-ROM) drive 112 are interconnected via an IEEE1394 cable on the basis of a point-to-point bus technique.
If any one of the nodes is removed from the IEEE1394 cable or a new node is added thereto under the above condition, the IEEE1394 serial bus is reset to be initialized. In the initialization procedure, the nodes connected to the IEEE1394 cable initialize existing information and are reassigned respectively with physical addresses.
Then, an IEEE1394 interface enters a standby state for the start of a normal operation.
On the other hand, the IEEE1394 interface supports both the asynchronous transfer mode and isochronous transfer mode as mentioned above.
In the asynchronous transfer mode, data and layer information are transferred on the basis of an address. But, in the isochronous transfer mode, data is transferred on the basis of a channel number, not the address. For example, the isochronous transfer mode may be used for the transfer of multimedia information considerably restricted by time, such as moving picture or voice data, and the asynchronous transfer mode may be used for the transfer of information from devices with no need for the real-time operation, such as the printer 108 and scanner 110. Protocols are assigned respectively to the nodes to support the data transfer thereof. For example, a protocol AV/C may be applied to the audio unit 100 and DTV 102 and a protocol Serial Bus Protocol-2 (SBP-2) may be applied to the CD-ROM/DVD-ROM drive 112. Also, a protocol DP Protocol may be applied to the printer 108. These protocols are distinguished from one another according to 1-bit flags and stored in protocol packet data in the associated nodes.
Each of the nodes sends self protocol identification packet data to the network to inform the other nodes of its data transfer and performs data transmission/reception with only certain ones of the nodes with the same protocol. In this manner, the nodes are interconnected via the IEEE1394 cable and transfer data in the asynchronous transfer mode or isochronous transfer mode.
However, the data transfer is not possible between certain ones of the nodes interconnected via the IEEE1394 cable, having different protocols, because of the presence of no interface therebetween. For example, in the case where the user loads a compact disk (CD) or a video CD with data compressed according to the MPEG-2 standard into the DVD-ROM or CD-ROM drive to watch a desired picture from the CD through any other video node than a personal computer (PC), such as the digital TV, the video reproduction is not effected due to different protocols.
At present, the DVD-ROM or CD-ROM drive is operated in the PC according to a SBP-2-based protocol, whereas the digital TV is standardized to have an AV/C-based protocol.
Therefore, the present invention has been made in view of the above problem, and it is an object of the present invention to provide a data transfer method based on inter-node protocol interfacing.
In accordance with one aspect of the present invention, in an IEEE1394 serial bus network having a plurality of nodes interconnected via an IEEE1394 cable, there is provided a method for performing a protocol interfacing operation for the nodes, comprising the first step of formatting a protocol identifier packet of each of the nodes upon initializing an IEEE1394 serial bus due to node addition or deletion; the second step of sending the formatted protocol identifier packet of each of the nodes to the other nodes; the third step of storing the protocol identifier packets of the nodes into a protocol map under control of a bus manager; the fourth step of sending a protocol query packet including a target node identifier from a source node among the nodes to the bus manager to request the transfer of data; and the fifth step of retrieving a communication protocol from the protocol map and sending a protocol set packet including information about the retrieved communication protocol from the bus manager to the source node and a target node among the nodes to perform the transfer of data between the source and target nodes through the communication protocol.
In accordance with another aspect of the present invention, in an IEEE1394 serial bus network having a plurality of nodes interconnected via an IEEE1394 cable, there is provided a method for performing a protocol interfacing operation for the nodes, comprising the first step of designating a specific node as a root node upon generation of a data transfer request from a source node among the nodes; the second step of sending protocol packet data from the source node to a destination node among the nodes; the third step of retrieving protocols of the source and destination nodes to set a communication protocol; and the fourth step of, if a common protocol is present for the source and destination nodes, setting the communication protocol to the common protocol and performing the transfer of data between the source and destination nodes through the communication protocol.